This application is based on patent application Hei. 11-7939 filed in Japan, the content of which are hereby incorporated by references.
1. Field of the Invention
This invention relates to a multi-point light measuring system including a plurality of light measuring units which can be disposed at different points for sensing optical characteristics at the different points at the same time.
2. Description of the Related Art
For example, in a performance evaluation of a projector, optical characteristics such as illuminance distribution and color distribution on a screen are measured. Furthermore, time-variation of the optical characteristic is measured for evaluating stability of a light source of the projector. On the other hand, in the art of architectural illumination, an effect of illumination is evaluated by measuring illuminance distribution in an illumination area. Furthermore, an effect of day light at the window side is evaluated by measuring time-valuation of the illuminance distribution.
In the conventional measurement of the illuminance distribution or the color distribution, a single light measuring apparatus such as an illuminance meter or a colorimeter is serially moved to a plurality of measurement points for measuring the illuminance or the color at each measurement point (repeating one-point measurement). Alternatively, a plurality of light measuring apparatuses are respectively disposed at a plurality of measurement points for measuring the illuminance or the color at each measurement point at the same time (method of multi-point measurement).
A light measuring apparatus such a illuminance meter and a colorimeter, in which a light measuring unit for receiving light rays is detachable from a main unit with a control circuit for controlling the light measuring operation and a display for displaying measurement data, is conventionally known and merchandized. By connecting the light measuring unit and the main unit by a dedicated cable, optical characteristics such as the illuminance and the color at a measurement point can be measured at a point distant from the measurement point.
Furthermore, a light measuring apparatus having output terminals for outputting measurement data to, for example, a personal computer for realizing a multi-point measurement is conventionally known and merchandized. In such a multi-point measurement system, the output terminals of a plurality of the light measuring apparatuses are connected by a generalized bus line such as GPIB (General Purpose Interface Bus) or a dedicated bus line to the personal computer serving as a data processing apparatus for transmitting the measurement data. The personal computer processes the measurement data from the measurement points transmitted through the bus line.
In the measurement of the optical characteristics such as the illuminance and the color, the multi-point measurement is suitable with regard to the quickness, the easiness and the concurrence (the same condition) of the measurement. However, the conventional light measuring apparatus in which the light measuring unit is detachable from the main unit cannot be used in the multi-point measurement, since only one light measuring unit can be connected to the main unit. In other words, it is impossible to connect a plurality of light measuring units by a cascade line connection to the main unit. Thus, a plurality of independent light measuring apparatuses are disposed at respective measurement points, and the light measuring apparatuses are connected to the personal computer by the bus line. The system will be complex and expensive.
An object of the present invention is to provide a multi-point light measuring system including a single main unit and a plurality of light measuring units connected by a cascade line connection.
A multi-point light measuring system in accordance with the present invention comprises: a plurality of light measuring units for receiving incident light and for obtaining data with respect to the incident light; a single main unit including a controller for controlling light measuring operation and a display; a plurality of first interface units respectively provided on the light measuring units and adjoining two first interface units are connected each other by a communication cable; a second interface unit provided on the main unit. The controller collects the data from at least one light measuring unit via the first and second interface units and the communication cable. The display displays a value of an optical characteristic based on the collected data.
By such a configuration, the data of an optical characteristic such as illuminance, color, color temperature, and so on at a plurality of measurement points can be obtained at the same time by the light measuring units which are connected by a cascade line connection of the first interface units. The multi-point light measuring system in accordance with the present invention is configured by a plurality of light measuring units and a single main unit, so that the system can be simplified and inexpensive.